Recovery of metals from ores



July 28, 1931. A. J. QUENEAU RECOVERY OF METALS FROM ORES Filed July 26.1928 www nventoz Patented July 28, 1931 4UNITED STATES PATENT OFFICE lAUGUSTIN LEON JEAN QUENEAU, or NEW Yomr, N. Y.

RECOVERY OF METALS FROM OBES Application led July 26, 1928. Serial No.295,517.

This invention relates to therecovery offore, to impede the travel ofthe charge..

through the retort. A11 important feature of my improved method involvescertain 15 purifying steps hereinafter more fully referred to wherebythe charge is treated so as to free it from those constituents of theore which tend to adhere to the side walls of the vertical retort. v

The most generally used zinc ores are sulfides. In the usual practice ofrecovering zinc from sulfide ores, the latter are roasted to eliminatesulfur and to obtain sulfuric acid as a by-product. In this treatment,the sulfur content of the ore is brought down to approximately 4 percentor less. The partly de-sulfurized ore is then usually sintered to bringdown the sulfur content to approximately three-fourths'of one percent. r

This sintered ore is usuall crushed to make a charge which will pass trough a half inch mesh screen. This charge is then mixed with about 40percent of coke breeze, anthracite fines or similar reducing materialand 35 is charged into retorts horizontally disposed in a gas-firedfurnace. The zinc is driven ofi' in the form of a vapor and recovered incondensers usually connected with the retorts. In this conventionalmethod of operation, the metal values (such as zinc) recovered isapproximately 86 percent of the total amount of the ore charge. Thiscon-- ventional retorting practice is essentially a batch process. Thatis to say, it is not a continuous operation. The charge is usuallyplaced in the retorts one morning and is not removed until the followingmorning and this prior practice calls for a comparatively large workingcrew whose duties are heavy and arduous and which'are performed in ahot, dusty and unhealthy atmosphere. Many trials and attempts have beenmade covering aperiod of aboutseventy years to 'provide a workablemethod 'for vthe continuous smelting of ores such as zinc or the like.in vertical retorts but as far as I am aware, these have provedunsuccessful. In Athe treatment of'ores it is my observation and beliefthat vertical retorts heretofore used have only been successivelyoperated on ores w of extreme purity, or by-products which contain noganguematerial. Heretofore vertical retorts could onlybe .used with zincbearing materials in which the gangue was of a non-slagging nature.

With the vertical retorting furnaces heretofore used, I have observedafter years of practical consideration of the matter that only pure zincbearing material such as galvanized skimmings could be treatedsuccessfully in practice, that is, with the downward travel of thecharge taking place unimpeded. And I have determined that the reason forthe failure ofthe vertical retort to be used in a continuous method ofsmelting zinc is doubtless due tothe tendency of the gangue materials toform accretions on the highly heated retort walls and thus prevent thecharge from-moving downward uniformly. Such downward travel of thecharge is an so essential requirement for continuous operation ofsmelting zinc in a vertical retort and as far as I am aware, I am thefirst to have devised a method of smelting the usual grade ofzinciferous or Similar ore in a vertical retort.

My novel method will be full apparent from the following description wen read in l connection with the accompanying drawing in which thesingle figure is a diagram illustrative of the method.

p Referring to the diagram, crushed sulfide ore is fed to a conventionalform of roaster 10 so as to drive off the sulfur which is recovered inthe usual manner in the form of sulfurie acid. `The roaster dischargesan ore product in which the sulfur is reduced to about 4 percent. Thisde-sulfurized ore is mixed, for example, as indicated, at the mixer 12with furnace residues obtained from the 100 rated from the gangue arereoxidizedand passed in the form of fume to a suitable electric dustprecipitator as indicated by the flow line 18. Alternatively theValuable roducts may be passed through a suitable ag-house; Thus, it isclear, that the valuable constituents of the charge are separated fromthe earthy gangue or Waste such as silica, lime, magnesia,l man aneseand heavy metals such as copper, nic el.,` etc., which is v dischargedas indicated by the flow line 22.

, sulfate or su The zinc oxide delivered to the precipitator 20 isusually contaminated by a small percentage of divided carbon and aproxif mately 2 or 3 ercent of sulfur in the orm of Hite and smallamounts of ash.

To further urify thecharge which is to be subsequently treatedcontinuously in a vertical retort furnace, I add coke breeze at thestation indicated at 24 in the `flow diaam. The mixture is then fed to asintermg machine 26 in which the charge is sub- 'ected tothe action of achloridizingagent.

he chlorine bearing material used may' be sodium chloride, calciumchloride or the like. By sinterino` the charge in the presence of sucha! chloridizing agent, I am enabled to effect substantially orapproximately a total elimination of the sulfur-content of the charge nomatter inwhat form the sulfur y such as coke breeze, anthracite linesor-the like, this additionv taking place as indicated diagrammaticallyat the station 30. AThe ratio vof reducing agent to the crushed chargemayvary. By way of example, I may add approximatel percent of reducing aent by weight.v is mixture of substantially pure zinc oxide and coke orsimilar reducing agent'is transferred as indicated by the flow line 32to the usual charging hopper 34 at the top of a vertical retort 14. Inthis retort the zinc oxide is reduced, resulting in the evolution ofcarbon monoxide and zinc vapor. The latter passes to the usual condenser36 and the zinc vapor condenses into molten zinc and the carbon monoxideburns to carbon dioxide at the mouth of the condenser. The orel chargedescendscontinuously through the vertical retort and adually becomeslower and lower in zinc va ue and when the charge reaches the lower partof the retort, it contains only a sm'all percentage of zinc. Theresidues are removed from the bottom of the retort together with theremaining large excess of the reducing fuel production per ton of metalis greatly re-V duced. Much heavy and unhealthy labor accompanying theoperation of the usual discontinuous retort furnaces is done away with.o

The method provides a practical solution of problems above mentionedwhereby a vertical retort furnace can be used for the continuoustreatment o f practically any type of zinc bear-v ing ore. f

From the description, it| will be apparent that not only the slagforming materials are removed from the ore butv also the sintered zincoxide produced is obtained free from the contaminating metals such ascadmium, lead,

etc., usually found in the zinc recovered in the horizontal retortinvfurnaces used in the conventional prior an present-day practice.

In my improved method as pointed out, the slag forming elements from thezincv oxide contents of the ore are practically totally eliminated, agreat bulk of the` impurities being eliminated in a rotar kiln and theremainder being eliminated by t e chloridizing sintering operation.

The sintered nodules carry only zinc oxide. This being true, it ispossible for the charge of zinc oxide and reducing agent to movedownward freely in' the vertical retort furnace as fas-t as the finalresidues are removed at the bottom of the retort. Thus, it is seen thatthe chargemay be fed in a continuous manner to the top of'the retort andthe residues may continuously be removed from the bottom thereof. Theexcess of carbon used in the vertical retort charge to maintain ,thej lscription vforming part of the specification are to be interprete in anillustrative rather than a limiting sense.

What I claim is 1. In the recovery of zinc fromits ores, the methodwhich consists in roasting a charge of ore to drive oi' sulphur, leadand cadmium products, mixing retort residues with the charge, subjectingthe mixture to heat in an oxidizing atmosphere and separating thedesired oxide from the gangue, subjecting the oxide to a chloridizingtreatment for purification, mixing a reducing agent with the purifiedoxide and passing said mixture of reducing agent and purified oxidevertically downward through a heated retort to condense the desiredrefined product.

2. In the recovery. of zinc from its ores,

the method which consists in roasting a charge of ore to drive offvolatile products, I adding a reducing agent to the charge, subjectingthe mixture to heat in an oxidizing atmosphere and separating theresulting oxide from the gangue, subjecting the oxide to a chloridizingsintering treatment to purify it, crushing the sintered mass and mixinga. reducing agent therewith, and charging the mixture of purified oxideand reducing agent to a vertical retort.

3. The method of claim 2 including the step of mixing the residues fromthe retort with. the charge subjected to treatment in the .oxidizinatmosphere.

4. n the recovery of zinc from sulfide ores, the method which consistsin roasting the ore, treating the roasted charge in a r`otary kiln, andseparating the zinc oxide from the gangue, sintering the oxide in thepresence of a chloridizmg agent to purify it, crushing the sintered massand mixing a reducing agent therewith, and charging the latter mixtureto a vertical retort and recoverin'g the refined zinc product bycondensay tion of the va ors in said retort. A

5. The met od of claim 4 includin the step of mixing of retortresidueswit the roasted chargetreated in said rotary kiln. Y 6. The methiod ofclaim 4 includin the step of mixing' of retort residues wit the roastedcharge treated Vin said rotary kiln, the said sintering .step includingsubjecting the oxide to purification by a chlorldizing agent.

7. The method of claim l1 characterized-by the fact that the charge iscontinuously passed through the vertical retort.

8. ,The method of claim 1 characterized by the fact that the charge iscontinuously passed through the vertical Aretort and the residues arecontinuously removed from the bottom of the retort.

VIn witness whereof, I have hereunto signed my name. I

" AUGUSTIN LEN JEAN QUENEAU.

